This CT-guided needle core biopsy is from a rapidly enlarging pelvic mass in a 48 y/o HIV+ male. The image shows high-grade neoplastic cells arranged in diffuse sheets. They have large vesicular nuclei, prominent nucleoli, and brisk mitotic activity (see higher magnification in the next image). An initial immunohistochemical panel consisting of CD45, CD20, CD79a, CD30, ALK-1, bcl-1, S-100 protein, HMB-45, cytokeratin AE1/AE3, EMA, and myeloperoxidase was negative. CD3 and CD5 showed scattered lymphocytes in the background. A subsequent panel showed strong positivity for CD38 and CD138 and focal weak positivity for lambda light chains. The final diagnosis was plasmablastic lymphoma.